How well can CNN for bounding box detection generalise?
I suggest you to go through the r-cnn paper or go through a tutorial on it . CNNs transform the image into high dimensional vector in their last layer , in case of classification this vector is sent to a "softmax" layer , in case of bounding box regression , four values :length , breadth , location of one of the points of the bounding box , are regressed from this vector , so if you use a cnn with one regression head you end up with one bounding box irrespective of the training set.